Impact on silica particle physical characteristics of co-condensed alkoxide precursors†

Abstract

Understanding the condensation process of two precursors in the Stöber process is crucial to enhance the complexity and applicability of silica hybrids. We present a simple and effective method to prepare functional silica hybrid particles with tunable properties through the co-condensation of tetraethoxysilane and an organoalkoxide precursor using a modified Stöber process. Three organoalkoxide precursors have been studied: (3-mercaptopropyl)triethoxysilane, (3-cyanopropyl)triethoxysilane, and (3-aminopropyl)triethoxysilane. All three investigated systems produce functional silica hybrid particles, as confirmed by various characterization techniques. Scanning transmission electron microscopy and nitrogen sorption analysis demonstrated that features such as the microstructure could be tailored by the careful selection of the second precursor. A drastic increase in the specific surface area can be obtained with 3cyanopropyltriethoxysilane: 270 m² g⁻¹ compared to 17 m² g⁻¹ in the unfunctionalized silica particles. Other important characteristics such as the degree of condensation and surface charge can also be influenced by precursor choice. The enhanced reactivity of 3-aminopropyltriethoxysilane yields a higher degree of particle functionalization. Nanoscale chemical mapping has been performed using energy-dispersive Xray spectroscopy and Auger spectroscopy. Homogeneous distribution of the functionalities within the hybrid particles occurs. The present work gives tools to easily tailor functional silica particles, thus providing simple ways to tune their properties to meet a wide range of applications.